This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. The following descriptions and examples are not admitted to be prior art by virtue of their inclusion in this section.
The present disclosure relates generally to pressure transducers. In particular, the present disclosure relates to piezoelectric pressure sensors that are suitable for applications relating to oil/gas industry.
Piezoelectric pressure transducers have a crystal resonator located inside a housing with electrodes. Environmental pressure and temperature are transmitted to the resonator, via the housing, and changes in the resonator are sensed and used to interpret the pressure and/or temperature. U.S. Pat. No. 3,617,780 discloses one example of pressure transducer having a quartz crystal resonator with single-mode oscillation. The quartz resonator is affected by both temperature and pressure such that some devices may not be suitable for use in environments where both temperature and pressure vary.
Some examples of pressure transducers having a quartz dual mode resonator are disclosed in the U.S. Pat. Nos. 4,419,600, 4,547,691 and 5,394,345, which are incorporated herein by reference in its entirety. In the dual-mode resonator, B-mode vibration is primarily only responsive to temperature whereas C-mode vibration is responsive to both temperature and pressure. Thus, by noting the change in frequency in both modes, temperature and pressure can be measured simultaneously.
Many advances in the science of quartz pressure/temperature transducers have been made in connection with oil/gas field applications. Transient or dynamic pressure measurements are routinely employed in the estimation of formation permeability, reservoir pressure, formation continuity, and reservoir boundaries. The pressures encountered during such the estimation can be greater than 20,000 psi. While making measurements, the transducers can be subjected to temperatures of approximately 175° C. or more over. In addition, a subterranean tool with a pressure transducer is connected to equipment on the ground surface via a telecommunication cable and operated under the ground in relatively long operation time. In such oil/gas field applications, there is a need for improved pressure transducers that are capable of measuring pressure more stably and accurately in high temperature and pressure environment.